Broadcasting systems based on home servers achieves program viewing that is not restricted by airtime, with a provision of a program storage device and a communication connecting function in a receiving device. Further, a content provider provides program-related information, called metadata, to achieve various broadcast services such as highlight program viewing. For example, such services include a service to allow a viewer to see only hitting scenes of a hitter as a digest of a baseball broadcast program. This service is achieved by a content provider who produces metadata including a program name indicative of a baseball broadcast program and information indicative of starting time points of all hitting scenes of the hitter and provides the metadata to a viewer. From the viewpoint of producing attractive metadata inexpensively, it is considered that metadata are produced not only by a content provider, but also by a network provider, a third party, or a user.
Meanwhile, falsification of metadata or production of unauthorized metadata may cause program use against content provider's intention, such as allowing a program to be viewed without any commercials or connecting scenes in a plurality of programs so as to generate another program. Accordingly, in order to prevent rampancy of unauthorized metadata, falsification of metadata should be prevented, and a content provider should be able to specify metadata permitted to be used for each program.
A reference discloses an outline of the standard of ARIB (Association of Radio Industries and Businesses) STD-B38 (Coding, Transmission and Storage Specification for Broadcasting Systems Based on Home Servers) and particularly illustrates a concept of broadcasting systems based on home servers (Reference: Standard outline (broadcasting field), Number of Standard: ARIB STD-B38, Name of Standard: Coding, Transmission and Storage Specification for Broadcasting Systems Based on Home Servers, [online], Association of Radio Industries and Businesses, [searched on Jan. 29, 2004], the Internet <URL: http://www.arib.or.jp/tyosakenkyu/kikaku_hoso/hoso_std-b038.html>).
The standard of ARIB STD-B38 defines a description method of metadata for a program in an XML (Extensible Markup Language) format. The standard of ARIB STD-B38 formulates the definitions not only for describing additional information on content in metadata and displaying the additional information on a playback terminal, but also for describing information for playback control such as a partial playback of content based on a description in metadata. With use of a playback device having a function of playing back content based on metadata, the content can partially be played back, or a digest of the content can be defined and played back without editing the content.
Here, since metadata are described by XML, anyone can readily generate metadata. Thus, anyone can readily generate a digest of content if the content is accessible. Accordingly, it has been necessary to provide an access control to content, for example, so that access is permitted from metadata produced by an author A but is not permitted from metadata produced by an author B.